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Affected by climatic conditions such as rainfall, evaporation and air temperature, most of the backfill soil is in an unsaturated state, and the decrease in matric suction leads to the failure of the retaining structure. In view of this, this study takes the vertical rigid retaining wall with narrow unsaturated backfill as the research object, assuming that the backfill behind the wall forms a circular soil arch and considering the interlayer shear stress; thus, the analytical solution of the active earth pressure of narrow unsaturated soil is derived based on the thin layer element method. The reliability of this method is verified by comparing with the experimental and existing theoretical results. A parameter analysis demonstrates that with the increase in the interface friction angle of the moving wall–soil, the average shear stress coefficient of zone I and zone II increases gradually, but with the increase in the interface friction angle of the fixed wall–soil, the average shear stress coefficient of zone I decreases; with the increase in effective internal friction angle and effective cohesion, the active earth pressure decreases and the tension crack depth increases; with the increase in the interface friction angle, the active earth pressure in the upper part of the retaining wall increases slightly, while the active earth pressure in the lower part decreases obviously; with the increase in matric suction, the active earth pressure first decreases rapidly and then increases gradually, and the tension crack depth first increases and then decreases, but the distribution pattern of the horizontal active earth pressure remains unchanged; the active earth pressure decreases with the decrease in the aspect ratio, and when the aspect ratio is smaller, the attenuation is more obvious; until the aspect ratio reaches a certain value, the active earth pressure is basically unchanged.

In this paper, a simple, rapid, solvent-free and low-cost method of pressurized hot water extraction (PHWE) followed by headspace solid-phase microextraction (HS-SPME) and gas chromatography-mass spectrometry (GC-MS) was developed for the analysis of essential oil in a traditional Chinese medicine (TCM) of the dried ripe fruit of Fructus Amomi (Sha Ren). The essential oil in the TCM (0.050 g) was extracted by water at 50 bar and 150 degrees C, followed by extraction and concentration by SPME fibers at 80 degrees C for 15min and analysis by GC-MS. The PHWE and HS-SPME parameters were optimized. Thirty-five compounds in the TCM were identified by PHWE-HS-SPME. Among them, camphor, an active compound, in the TCM samples was quantitatively analyzed. The proposed method required little time to prepare the sample. Moreover, little sample mass and no organic solvent was needed. The precision of the present method was found to be good (R.S.D.10.0%). It is shown that PHWE-SPME-GC-MS is an alternative method for the determination of volatile components in TCMs and can be used as a powerful tool for TCM quality assessment.

Four sampling techniques, solid-phase microextraction (SPME), supercritical fluid extraction (SFE), steam distillation (SD), and solvent extraction (SE), were compared for the analysis of volatile constituents from a traditional Chinese medicine (TCM) of the dried ripe fruit of Fructus Amomi (Sha Ren). A total of 38 compounds were identified by gas chromatography/mass spectrometry. Different SFE and SPME parameters (modifier content, extraction pressure, and temperature for SFE and fibers, extraction temperature, and time for SPME) were studied. The results by SFE and SPME were compared with those obtained by conventional SD and SE methods. The results showed that SFE and SPME are better sample preparation techniques than SD and SE. Due to SFE's requirement for expensive specialized instrumentation, the simplicity, low cost, and speed of SPME make it a more appropriate technique for extraction of volatile constituents in TCMs.

Flos Chrysanthemi Indici is a common traditional Chinese medicine (TCM). In this paper, headspace solid-phase microextraction coupled with gas chromatography-mass spectrometry (HS-SPME-GC-MS) was developed for quality assessment of Flos Chrysanthemi Indici from different growing areas in China. SPME parameters such as extraction fibers, extraction temperature, extraction time and sample mass were investigated to achieve identical results to those obtained by the steam distillation (SD). The selected SPME conditions were as follows: SPME fiber coated with 65-microm PDMS/DVB, extraction temperature of 60 degrees C, extraction time of 30 min and sample mass of 1.0 g. Furthermore, four active compounds (eucalyptol, camphor, borneol and bornyl acetate) presented in the TCM were applied to evaluating the quality of Flos Chrysanthemi Indici from 20 various areas. The quality assessment was successfully performed to compare the similarity value (S) between different sample vector of Flos Chrysanthemi Indici and the standard profile vector (SPV). The results showed that the proposed HS-SPME-GC-MS was an alternative technique for quality assessment of Flos Chrysanthemi Indici samples.

Headspace solid phase microextraction coupled with gas chromatography-mass spectrometry (HS-SPME-GC-MS) has been applied to the determination of the volatile compounds of a common traditional Chinese medicine , Flos Chrysanthemi indici. Twenty-six compounds were identified by the present method, which are similar to the results from steam distillation. Difference in analysis from ten growing areas was found to be in their relative content and total concentrations. Four active compounds (cineole, 3-thujanone, borneol and bornyl acetate) were applied to the evaluation of the quality of Flos Chrysanthemi indici from different areas. By comparing their peak areas, it was found that Flos Chrysanthemi indici with the best quality was from Hangzhou in China. These results show that HS-SPME-GC-MS is a simple, rapid and solvent-free method for the analysis of the volatile compounds in this material and a potential tool for its quality assurance.